Methods of introducing fuel into an internal combustion engine and devices therefor

ABSTRACT

The invention relates to a method permitting operation of internal combustion engines without using conventional ignition systems and without requiring such heavy fuel feed pumps as are necessary in diesel engines, or the complicated injection means required in engines with direct fuel injection against high compression pressure in the cylinders. The present invention makes use of fuel chambers communicating with the cylinders through valve-controlled ports which can be opened and closed in the same way as conventional intake and exhaust valve ports in dependence on the rotation of the crankshaft and which are opened to the combustion chambers in the engine cylinders at a suitable point of time within a period immediately before and after completion of a compression stroke and are closed after initiation of a suction stroke for evacuating the fuel chambers for reducing the pressure and for a certain cooling of the valves.

United States Patent [191 Nilsson Oct. 16, 1973 METHODS OF INTRODUCINGFUEL INTO AN INTERNAL COMBUSTION ENGINE AND DEVICES THEREFOR [21] Appl.No.: 178,602

[30] Foreign Application Priority Data Sept. 10, 1970 Sweden 12313/70[56] References Cited UNITED STATES PATENTS 4/1947 Stickney 123/33 VC4/1950 Ziegler 123/33 D 3,507,261 4/1970 Myers et a1. 123/32 ST3,580,231 5/1971 Brodbury 123/32 K FOREIGN PATENTS OR APPLICATIONS 2,5752/1908 Great Britain 123/33 VC 14,845 9/1913 Great Britain 123/33 VCPrimary Examinerl.aurence M. Goodridge Assistant Examiner-Cort FlintAttorney-Ralph E. Bucknam et al.

[ 5 7] ABSTRACT The invention relates to a method permitting operationof internal combustion engines without using conventional ignitionsystems and without requiring such heavy fuel feed pumps as arenecessary in diesel engines, or the complicated injection means requiredin engines with direct fuel injection against high compression pressurein the cylinders. The present invention makes use of fuel chamberscommunicating with the cylinders through valve-controlled ports whichcan be opened and closed in the same way as conventional intake andexhaust valve ports in dependence on the rotation of the crankshaft andwhich are opened to the combustion chambers in the engine cylinders at asuitable point of time within a period immediately before and aftercompletion of a compression stroke and are closed after initiation of asuction stroke for evacuating the fuel chambers for reducing thepressure and for a certain cooling of the valves.

10 Claims, 4 Drawing Figures PATENTFUUU 16 1975 3,765,381

SHEET 10F 3 FIG! WENTEDUET 16 1975 SHEET 2 BF 3 METHODS OF INTRODUCINGFUEL INTO AN INTERNAL COMBUSTION ENGINE AND DEVICES THEREFOR The presentinvention relates to a method of introducing fuel into the combustionchamber of the cylinder or each of the cylinders of an internalcombustion engine, in which air for the combustion is compressed duringthe working cycle of the engine to reach a high pressure during acompression stroke prior to each power stroke, said fuel beingintroduced into the combustion chamber at or near the end of thecompression stroke from a fuel chamber separated from the combustionchamber by means of a sluice valve.

lt is already known to arrange auxiliary chambers in communication withthe combustion chambers of combustion engines through a valve which isopened at the end of the compression stroke and closed at the end of thepower stroke or at an earlier point of time. The purpose of this is toallow the air compressed to high pressure in the respective cylinder torush into the auxiliary chamber in order to ignite the fuel andtransport the fuel from the auxiliary chamber to the cylinder.Previously known devices and their mode of operation have, however,serious drawbacks making them impossible for practical use. A seriousobstacle is, for example, the risk of overheating the sluice valve whichmust remain open during a substantial part of the power stroke andtherefore is exposed to strong heating during the combustion stage.Another drawback is that feeding of fuel into the auxiliary chamber ismade more difficult due to pressure rising in the auxiliary chamber whenthe fuel comes into contact with the hot walls of the auxiliary chamber.Attempts have been made to overcome this inconvenience by placing theauxiliary chamber at a long distance from the cylinder but this solutionhas proved impossible in practice due to the fact that the fuel willhave to travel far too long to reach the cylinder chamber in modernengines operating at a high rpm. The invention has for its object tosolve these problems in order thereby to permit the operation ofcombustion engines without requiring any conventional complicatedignition systems which are used in carburettorfed engines, or the heavyfuel feed pumps in diesel engines.

This object has now been realized through the method of this inventionwherein for each working cycle of the engine a fuel portion adequate toone power stroke is introduced from a source of fuel into acomparatively small, closed space near the combustion chamber in thecylinder or each cylinder, communication is established between thisspace and the respective combustion chamber at the end of thecompression stroke for the cylinder in question to admit compressed airfrom the cylinder into said space for mixing with the fuel and forejecting this to the combustion chamber under such conditions that thefuel/air mixture formed is ignited at the same time, and the pressure insaid space is reduced before the next fuel portion is fed.

According to a further development of the invention, said space may bekept open to the cylinder chamber via the sluice valve during at leastthe first part of the suction stroke in the cylinder, in order to bringabout a pressure drop before each feeding of a new fuel portion. Anotherimprovement can be made by arranging the air flow passages so as toprovide during the suction stroke a flow of air around the sluice valvefor cooling this valve.

For carrying the. invention into effect, the invention also comprises acombustion engine which may have one or more cylinders and conventionalair intake and exhaust valves for each cylinder. The engine according tothe invention is equipped with a fuel chamber arranged in closeconnection with the combustion chamber in the cylinder or each cylinder,said fuel chamber being connected to a source of fuel and adapted,before the end of each compression stroke in the cylinder, to receivefrom the fuel source a fuel portion adequate to the power stroke in thecylinder, and to be connected to the combustion chamber in the cylinderthrough a communication which is adapted to be closed by the sluicevalve and to be opened for connecting the fuel chamber to the combustionchamber at or near the end of each compression stroke to admit hotcompressed air from the combustion chamber to the fuel in the fuelchamber under such conditions that the fuel portion in the fuel chamberwill be mixed with the compressed hot air under such pressure andtemperature conditions that the mixture will be ignited and ejected intothe combustion chamber for bringing about the power stroke in thecylinder, said engine further comprising means for decreasing thepressure in the fuel chamber before each new feed of a fuel portion intothis chamber.

According to a preferred embodiment the pressure decreasing meanscomprises a valve means adapted to bring the fuel chamber intocommunication with a point of the air intake and exhaust system of theengine where a comparatively low pressure prevails during at least partof the suction stroke. This valve means may consist of or comprise thesluice valve and is adapted to be regulated by a valve control mechanismdriven by the camshaft, and said point, where a comparatively lowpressure prevails, may be the cylinder chamber during the first part ofthe suction stroke.

The invention makes it possible to mix, for example, inflammable fuelinto high-compressed air in the engine cylinders in that the fuel is fedunder the most favourable pressure conditions into the fuel chamberswhich communicate with the cylinders through valve controlled portswhich can be opened and closed in the same manner as the conventionalintake and exhaust valve ports of the engine in dependence upon therotation of the camshaft, said fuel chambers being opened to thecombustion chambers in the respective engine cylinders at an optimumpoint of time within the period immediately before and after thecompression stroke is completed. The air having been compressed to highcompression in the respective combustion chamber rushes into therespective fuel chamber and is mixed with fuel contained therein. Thefuel is gasified and the mixture is ignited while rushing into thecombustion chamber under the action of strong turbulence which ariseswhen the gas particles are ignited when coming into contact with theheated air. Thus, a spontaneous ignition is effected as a result oftemperature and pressure and it should be noticed that the air in therespective cylinder can be compressed to a very high pressure even'wheninlammable highor low-octane fuels are used and substitute therefor:Preignition of the fuel is avoided because the fuel is not exposed tothe compression pressure until it is mixed with air, which mixing takesplace when the valve-controlled fuel port is opened exactly at the rightmoment of ignition Despite a high compression pressure, there is no needfor using those heavy pressure pumps which are necessary in conventionaldiesel engines in which the feed of fuel is effected against the highpressure in the combustion chambers, because the fuel is first fed intoa fuel chamber in which the pressure is low. As the fuel chambers arepositioned close to the respective combustion chambers the flow passagesbecome short and as the pressure in the fuel chambers is decreasedbefore the feeding of the fuel portions the fuel chambers may have acomparatively small volume, which makes it possible to operate theengine at a relatively high rpm.

The invention will be described more fully below with reference to theaccompanying drawings, in which:

FIG. 1 is a schematic vertical cross sectional view of part of acombustion engine according to the invention, equipped with twocrankshaft driven camshafts for the valve control;

FIG. 2 is a similar view of an engine according to the invention wherethe valves have been positioned somewhat differently;

FIG. 3 is a top plan view of part of the engine of FIG. 2 with a topcover removed; and

FIG. 4 is a vertical sectional view of the top of a per se known dieselengine as reconstructed according to the invention.

The engine as shown in FIG. 1 is provided in a generally conventionalmanner with an inlet valve 1 and an outlet valve (concealed in FIG. 1)for each cylinder but in accordance with the present invention it isalso equipped with a third valve 3 adapted to open and close acommunication between a fuel chamber 5 provided in the cylinder head,said chamber being adapted to serve as a sluice for the transfer of fuelfrom a fuel source under pressure and for this purpose said chamber isconnected to said fuel source (not shown) through a pipe 6. Theadditional valve 3, which thus serves as a sluice valve, issubstantially of the same design and has substantially the samemechanical mode of function as the conventional inlet valve 1, and thesluice valve port 7 between the fuel chamber 5 and the combustionchamber 8 in the cylinder is also of the same design as the conventionalinlet port of the embodiment shown in FIG. 1. The fuel feed or sluicevalve 3 isregulated by means of a common valve operating mechanism whichincludes one 9 of the two camshafts 9, 9' of the engine which are drivenin a conventional manner by means of the crankshaft 10.

The inlet valve 1 is adapted to admit air from the air intake pipe 11and the outlet valve (2 in FIG. 3) is adapted to let out the exhaustgases to the exhaust pipe 12 in a conventional manner.

In FIG. 1 the engine piston 14 is shown at its upper turning-pointposition on its way downwards, just as the sluice valve 3 has opened.High-compressed air from the combustion chamber 8 and gas, which hasbeen produced from the fuel in the fuel chamber 5 by heating'from thecylinder head, are mixed with each other in the combustion chamber 8 andin the fuel chamber 5 under strong turbulence produced by the pressuredifference and the pressure equalization between the fuel chamber 5 andthe combustion chamber 8, and by contact with the hot high-compressedair in the'combustion chamber the fuel is ignited in a very short timethroughout the gaseous mass.

In low-octane fuels the ignition perhaps tends to be carried through toorapidly but this can be prevented by dimensioning the valve portdiameter with respect to the type of fuel concerned and the ignitionspeed desired. Another possible way is to control the movement of thevalve 3 so that it opens and closes the sluice valve port 7 according toan optimum movement pattern which can be defined by the form of thecorresponding cam 15 on the camshaft 9. By comparatively easily realizedmodifications the invention can thus be adapted to suit most types offuel from common high-octane fuels used for high-compressedcarburettor-fed engines, or diesel oil used in common diesel engines, tolow-octane fuel, such as engine kerosene or illuminating kerosene, orliquified petroleum gas or other gaseous fuel.

To prevent the pressure in the fuel chamber 5 from spreading via thecombustion chamber 8 to the fuel pipe 6 when the valve 3 is open, anon-return valve 16 is arranged at the inlet of the fuel pipe into thefuel chamber 5. The feeding of the fuel portions into the fuel chambers5 of the engine takes place intermittently during a very short time andin operation no significant back-pressure will arise due to gasificationof fuel in the fuel chamber heated by the engine. Thus, the supply offuel to the fuel chambers 5 can be effected pulsatingly at acomparatively low pressure by means of a simple pump and, for instance,an electronically controlled injection means in such a way that thepulse length exactly defines the quantity of fuel injected per pulse andso that this quantity will be in proper relation to the engine load. Thefuel valves 3 can be sealed in substantially the same way asconventional inlet valves or according to other known sealing methodsand the cooling of the valve 3 which in the embodiment shown is exposedto high heat from the combustion chamber, can likewise be carried out ina conventional manner, for instance in accordance with known principlesfor the cooling of aircraft engine valves. The third valve will be openduring the power stroke, during the exhaust stroke and during asubstantial part of the suction stroke and is not entirely closed untilthe suction stroke has been completed (see the form of the cam 15 on thecamshaft 9), for which reason the valve 3 during the suction stroke or asubstantial part thereof is cooled by inflowing cold air. This reducesthe heat problem considerably.

From the foregoing it appears that no specific ignition device isrequired for the engine according to the invention. The compressedheated air in the respective combustion chamber ignites spontaneouslythe fuel which has been gasified in the fuel chamber 5 by heat producedby the engine. If the engine is water-cooled, the water-cooling may beutilized for controlling the temperature of the chamber 5.

The engine shown in FIG. 2 corresponds to the engine of FIG. 1 but showsmore clearly how the fuel pipe is introduced into the cylinder headthrough a passage 20 including the non-return valve 16. According to theembodiment of FIG. 2, the three valves 1, 2 and 3 for a cylinder arealigned in the longitudinal direction of the engine while in FIG. 1 itis assumed that the corre sponding valves are positioned on the cornersof a triangle.

Various modifications of the valve structures in the illustratedembodiments of the engine according to the invention are of courseconceivable within the scope of the invention. The embodiment of thesluice valve 3 is therefore only to be regarded as an example of theinvention, as is also the valve control arrangement. A single camshaftwith a suitable cam means may of course be used instead of twocamshafts.

It should be noticed (see the form of the cam in FIG. 1) that the fuelchambers 5 are kept open during the power strokes in the correspondingcylinder and during the time the exhaust valves are open for the exhauststrokes and that the gas pressure, which is conveyed to the fuelchambers during the power strokes, is thus reduced prior to the nextfeed of fuel into the respective sluice chamber so that this feedingdoes not meet any noticeable resistance or, anyway, not any substantialresistance. Of course, another means is conceivable for bringing about apressure drop in the fuel chambers, and under certain circumstances itis of course also possible considerably to shorten the opening times forthe valves 3 either these are controlled by the camshaft via cams or insome other way by the power strokes of the engine.

The engine shown in FIG. 4 is a four-cylinder diesel engine of knowndesign reconstructed according to the invention. Originally this enginewas provided with a fuel injection nozzle for each cylinder. Accordingto the invention these nozzles are replaced by fuel chambers and sluicevalves, and the passages originally arranged for the injection nozzleshave been utilized for this purpose. No detailed description of the modeof operation of this engine would seem to be necessary since inprinciple it agrees with the engine of FIG. 1. For this reason it shouldonly be mentioned that the engine has an overhead camshaft 50 whichaccording to the invention is provided with a divided cam sleeve 51, arocker 52 on a shaft 53 and s sluice valve 3' with a spindle 54 which isslidably mounted in a sleeve 55 mounted in a bore in the cylinder head56. The rocker 52 cooperates with the cam sleeve 51 and with a head 57on the extreme end of the valve spindle 54 which is loaded by a spring58 for closing the valve member 3 against a valve seat 59 opening intothe cylinder chamber. Provided on the spindle between the guide sleeve55 for the valve spindle and the spindle head 57 is a valve sealingspring 60 which via a plate 61 maintains an O-ring 62 engaged with theextreme end of the guide sleeve 55 around the valve spindle. A fuelconduit (not shown) corresponding to the conduit 6 of FIG. 1 isconnected via a bore 63 in the cylinder head and an aperture 64 in aninsertion sleeve 65 to the interior of this sleeve which is mounted in alower part of the bore in which the sleeve 55 and the sluice valve aremounted. The insertion sleeve 65 forms a fuel chamber 5' correspondingto the chamber 5 of FIG. 1, and the lower end of the insertion sleeve 65forms the valve seat 59 of the sluice valve 3'. The insertion sleeve 65is closely connected with the cylinder head at 66 and with a projection55 of the guide sleeve 55, which sleeve is clamped in the bore thereforin the cylinder head by means of a bushing 67 screwed into a threadedpart of this bore, which bushing retains the guide sleeve 55 and theinsertion sleeve 65 in position. Thus, the bushing 67 and the twosleeves 55, 65 and the entire sluice valve are arranged so as to berapidly disassembled.

A further modification of the diesel engine shown in FIG. 4 comprises anew bracket 68 for the valve operating mechanism and a changed cover 69.

In the fuel passage 63 a non-return valve may be arranged to preventreverse flow of fuel.

In the embodiment of FIG. 4, the valve 3' is opened in upward directionfor admitting compressed air from the cylinder through the passage 70and for readmitting ignited fuel/air mixture through this passage 70into the cylinder. The passage 70 corresponds to the passage used in theknown diesel engine for injecting fuel into the cylinder from aninjection nozzle.

In the embodiment of FIG. 4 the volume of the fuel chamber 5 may bereadily changed by exchanging the insertion sleeve 65 for adjusting theengine to the working conditions desired.

The fuel supply to the fuel chamber 5' can be regulated by means of aconventional control means for controlling a valve, a pump or the like.

By keeping the valve 3 open during the exhaust stroke and during atleast part of the suction stroke, two advantages are obtained, viz., onone hand, cooling of the valve and, on the other hand, evacuation ofgases and pressure reduction in the fuel chamber 5 It is also possibleby means of a valve arrangement to connect the fuel chamber 5 with theintake system of the engine for sucking the air or part of the air intothe cylinder at the suction stroke, whereby an efficient cooling isobtained. This valve may be positioned in a passage between the fuelchamber 5' and the suction pipe of the engine andit can be operated by acam means in cooperationwith the camshaft 50. The practical arrangementof such a communication between the chamber 5 and the air intake systemof the engine may vary in dependence on the construction of the engine,and this arrangement does not seem to call for any further descriptionto anyone skilled in the art but it may be mentioned that in theconstruction shown in FIG. 4 such a valve-controlled air introductionpassage to the cylinder chamber via the fuel chamber 5' should open intothe fuel chamber 5' so that an efficient cooling of the valve will beobtained. The air introduction passage may, for instance, open into thechamber 5' at the upper end of the projection 55' on the guide sleeve 55through a set of channels 7], 71', as indicated by dotand-dash lines inFIG. 4.

What I claim and desire to secure by Letters Patent 1. In the combustionof fuel in an internal combustion engine which comprises atleast onecylinder pro vided with an air inlet and an exhaust and wherein com--pressed air ignites the fuel, the gas expands doing work and exhaustgases are removed during the cycle of suction stroke, compressionstroke, power stroke and exhaust stroke, a method of introducing fuelinto the combustion zone at or near the end of each compression strokein said cylinder, comprising the steps of introducing fuel into a fuelchamber located in the proximity of the combustion zone in saidcylinder, in an amount adequate for one power stroke, when the com-.munication between said combustion zone and said fuel chamber is closed,opening the communication between said fuel chamber and the combustionzone at the end of each compression stroke in said cylinder to admitcompressed air from the said cylinder into'said fuel chamber, mixingsaid compressed air with the fuel,

the mixture ignite and keeping said communication continuously open upto and during at least the initial portion of the following suctionstroke to secure optimal pressure drop prior to introduction of anotherportion of fuel, while securing evacuation of gases from said fuelchamber and while establishing a current of fresh cooling air in theproximity of the communication between said fuel chamber and saidcombustion zone.

2. A combustion engine which comprises at least one cylinder, air inletmeans and exhaust means, a fuel chamber in the proximity of thecombustion chamber in said cylinder, a passageway between said fuelchamber and said combustion chamber, valve means operable to open andclose said passageway, a fuel source with means for introducing a fuelportion into said fuel chamber for each power stroke in the cylinder,said valve means being adapted to open and close said passageway onlyonce for each cycle of the engine such that said passageway is opened atthe end of each compression stroke and closed before the beginning ofeach subsequent compression stroke, said fuel introducing means beingadapted to introduce fuel into said fuel chamber when the passagewaybetween said fuel chamber and said combustion chamber is closed, saidvalve means when open being adapted to introduce hot compressed air fromthe combustion chamber into the fuel chamber and to deliver the fuel/airmixture to the combustion chamber under such pressure and temperatureconditions that the mixture self-ignites, said valve means being adaptedto be kept continuously open up to and during at least the initialportion of the suction stroke whereby evacuating fuel chamber beforeeach introduction of a new fuel portion.

3. A combustion engine as claimed in claim 2 wherein said valve meanscomprise a sluice valve.

4. A combustion engine which operates according to the cycle of suctionstroke, compression stroke, power stroke and exhaust stroke, comprisingat least one cylinder, air inlet means and exhaust means,-a fuel chamberarranged in the proximity of the combustion chamber in said cylinder, afuel source, means for introducing one fuel portion into said fuelchamber for each power stroke in the cylinder, operable to open andclose a passageway between said fuel chamber and said combustionchamber, said valve means including a valve controlled by the engine andadapted to operate said valve to open and close said passageway onlyonce for each cycle of the engine such that said passageway is opened atthe end of each compression stroke and closed well in time before thebeginning of each next compression stroke, said fuel introducing meansbeing adapted to introduce fuel into said fuel chamber when thepassageway between said fuel and combustion chambers is closed, wherebythe fuel chamber. each time said passageway is opened, receivesrelatively hot compressed air from the combustion chamber and deliversthe fuel portion to the air for producing a fuel/air mixture under suchpressure and temperature conditions that the mixture is self-ignited,said valve means being adapted to evacuate said fuel chamber prior tointroduction of another fuel portion therein and means for cooling saidvalve means during at least the beginning of the suction stroke, beforesaid valve means are closed again. i

5. The engine according to claim 4 wherein said valve means comprise asluice valve which is adapted to be closed at a point of timeimmediately after the lowest pressure has been attained in saidcombustion chamber and in said fuel chamber.

6. A method as claimed in claim 1 wherein a valve is located in saidcommunication and the intake air for said cylinder is brought intocontact with the valve during at least part of the suction stroke in thecorresponding cylinder.

7. A combustion engine as claimed in claim 2, wherein the fuel chamberis connected with the fuel source by means of a fuel conduit via anon-return valve adapted to transmit fuel to the fuel chamber and toprevent backward flow of fuel and gas from the fuel chamber towards thefuel source.

8. A combustion engine as claimed in claim 2, wherein the means forreducing the pressure in the fuel chamber each time the chamber has beencaused to deliverv a fuel portion to the corresponding combustionchamber, includes a means, eg a camshaft and a cam, which is driven bythe crankshaft of the engine and adapted to bring the fuel chamber intocommunication with a point for relatively low pressure in the air intakesystem by keeping a closable communication passage between this systemand the fuel chambers open during at least the first part of the suctionstroke.

9. A combustion engine as claimed in claim 3, wherein the fuel chamberand the sluice valve arranged for opening and closing the communicationbetween the fuel chamber and the corresponding combustion chamber areadjusted to low-octane fuel, with respect to dimensions and openingtime.

10. A combustion engine as claimed in claim 3, wherein the sluice valveis adapted to be closed at a point of time immediately after the lowestpressure has been attained in the corresponding combustion cham ber and,consequently, in the fuel chamber.

* =l= :k a]:

1. In the combustion of fuel in an internal combustion engine whichcomprises at least one cylinder provided with an air inlet and anexhaust and wherein compressed air ignites the fuel, the gas expandsdoing work and exhaust gases are removed during the cycle of suctionstroke, compression stroke, power stroke and exhaust stroke, a method ofintroducing fuel into the combustion zone at or near the end of eachcompression stroke in said cylinder, comprising the steps of introducingfuel into a fuel chamber located in the proximity of the combustion zonein said cylinder, in an amount adequate for one power stroke, when thecommunication between said combustion zone and said fuel chamber isclosed, opening the communication between said fuel chamber and thecombustion zone at the end of each compression stroke in said cylinderto admit compressed air from the said cylinder into said fuel chamber,mixing said compressed air with the fuel, ejecting the mixture into thecombustion zone, letting the mixture ignite and keeping saidcommunication continuously open up to and during at least the initialportion of the following suction stroke to secure optimal pressure dropprior to introduction of another portion of fuel, while securingevacuation of gases from said fuel chamber and while establishing acurrent of fresh cooling air in the proximity of the communicationbetween said fuel chamber and said combustion zone.
 2. A combustionengine which comprises at least one cylinder, air inlet means andexhaust means, a fuel chamber in the proximity of the combustion chamberin said cylinder, a passageway between said fuel chamber and saidcombustion chamber, valve means operable to open and close saidpassageway, a fuel source with means for introducing a fuel portion intosaid fuel chamber for each power stroke in the cylinder, said valvemeans being adapted to open and close said passageway only once for eachcycle of the engine such that said passageway is opened at the end ofeach compression stroke and closed before the beginning of eachsubsequent compression stroke, said fuel introducing means being adaptedto introduce fuel into said fuel chamber when the passageway betweensaid fuel chamber and said combustion chamber is closed, said valvemeans when open being adapted to introduce hot compressed air from thecombustion chamber into the fuel chamber and to deliver the fuel/airmixture to the combustion chamber under such pressure and temperatureconditions that the mixture self-ignites, said valve means being adaptedto be kept continuously open up to and during at least the initialportion of the suction stroke whereby evacuating fuel chamber beforeeach introduction of a new fuel portion.
 3. A combustion engine asclaimed in claim 2 wherein said valve means comprise a sluice valve. 4.A combustion engine which operates according to the cycle of suctionstroke, compression stroke, power stroke and exhaust stroke, comprisingat least one cylinder, air inlet means and exhaust means, a fuel chamberarranged in the proximity of the combustion chamber in said cylinder, afuel source, means for introducing one fuel portion into said fuelchamber for each power stroke in the cylinder, operable to open andclose a passageway between said fuel chamber and said combustionchamber, said valve means including a valve controlled by the engine andadapted to operate said valve to open and close said passageway onlyonce for each cycle of the engine such that said passageway is opened atthe end of each compression stroke and closed well in time before thebeginning of each next compression stroke, said fuel introducing meansbeing adapted to introduce fuel into said fuel chamber when thepassageway between said fuel and combustion chambers is closed, wherebythe fuel chamber, each time said passageway is opened, receivesrelatively hot compressed air from the combustion chamber and deliversthe fuel portion to the air for producing a fuel/air mixture under suchpressure and temperature conditions that the mixture is self-ignited,said valve means being adapted to evacuate said fuel chamber prior tointroduction of another fuel portion therein and means for cooling saidvalve means during at least the beginning of the suction stroke, beforesaid valve means are closed again.
 5. The engine according to claim 4wherein said valve means comprise a sluice valve which is adapted to beclosed at a point of time immediately after the lowest pressure has beenattained in said combustion chamber and in said fuel chamber.
 6. Amethod as claimed in claim 1 wherein a valve is located in saidcommunication and the intake air for said cylinder is brought intocontact with the valve during at least part of the suction stroke in thecorresponding cylinder.
 7. A combustion engine as claimed in claim 2,wherein the fuel chamber is connected with the fuel source by means of afuel conduit via a non-return valve adapted to transmit fuel to the fuelchamber and to prevent backward flow of fuel and gas from the fuelchamber towards the fuel source.
 8. A combustion engine as claimed inclaim 2, wherein the means for reducing the pressure in the fuel chambereach time the chamber has been caused to deliver a fuel portion to thecorresponding combustion chamber, includes a means, e.g. a camshaft anda cam, which is driven by the crankshaft of the engine and adapted tobring the fuel chamber into communication with a point for relativelylow pressure in the air intake system by keeping a closablecommunication passage between this system and the fuel chambers openduring at least the first part of the suction stroke.
 9. A combustionengine as claimed in claim 3, wherein the fuel chamber and the sluicevalve arranged for opening and closing the communication between thefuel chamber and the corresponding combustion chamber are adjusted tolow-octane fuel, with respect to dimensions and opening time.
 10. Acombustion engine as claimed in claim 3, wherein the sluice valve isadapted to be closed at a point of time immediately after the lowestpressure has been attained in the corresponding combustion chamber and,consequently, in the fuel chamber.